Stabilization of the spine generally utilizes implants such as screws, cages, hooks, spacers, and other devices, to stabilize two or more adjacent vertebrae. Traditionally, two adjacent vertebrae are fixed to each other in a stable, mutual position, and fusion is induced by means of bone growth. Recently, dynamic stabilization of the spine has also been introduced, in which two vertebrae are stabilized but not fused, so that the relative motion between the vertebrae is preserved. In both cases, however, implants are used to maintain the relative posture of the two vertebrae.
A common procedure for spine stabilization uses pedicle screws on either side of the spine and a cage, where the pedicle screws and a connected rod support the spine posteriorly, while a cage inserted into the disc space provides support at the anterior side of the adjacent vertebrae. The cage may be inserted in a number of different ways, the most common currently in use including:    (i) anteriorly, in a procedure known as Anterior Lumber Interbody Fusion (ALIF),    (ii) posteriorly in a procedure known as Posterior Lumber Interbody Fusion (PLIF), or    (iii) lateraly in a procedure known as Transforaminal Lumber Interbody Fusion (TLIF).
Other options also exist, but with the exception of the procedure known as Axial Lumbar Interbody Fusion (AxiaLIF®) developed by Trans1 Inc of Wilmington, N.C., USA, all the other approaches reach the disc space within the transverse plane. The AxiaLIF® procedure has been described as useable between only one or two lumbar levels, with only the L5-S1 fusion procedure being publically advertised.
In U.S. Pat. No. 7,241,297 to S. M. Shaolian et al., there are described methods of inserting elements intervertabrally through a curved passage drilled from the pedicle to the intervertebral space. In order to negotiate such a narrow curved passage, tightly coiled elements of shape memory material are used. No additional screw support between the vertebrae is provided, such that only compression forces are handled by this method.
Reference is now made to FIG. 1, which is a cut-away drawing illustrating schematically a suggested procedure known as Trans-Pedicular Lumbar Interbody Fusion (TPLIF) also termed Guided Oblique Lumbar Interbody Fusion (GOLIF), in which the approach is oblique, from the pedicle 10 of an inferior vertebra 12 through the disc space 13 and into the adjacent superior vertebra body 14. The use of this angular oblique entry enables the screw to connect both vertebrae with a straight screw 16, which has a thread which is driven into the superior vertebra body 14, and is affixed at its other end preferably by means of a threaded fixture into the pedicle 10 of the inferior vertebra. One such screw is inserted on either side of the spine. Specific implementations of the GOLIF method are described in co-pending Provisional Patent Application No. 61/193,441 for “Guided Oblique Spinal Inter-body Fusion” and No. 61/193,586 for “Double Threaded Orthopedic Screw”, both having co-inventors with the present application.
Additional support for this fixation method, when needed, may be obtained using an intervertebral body such as a cage. However, insertion of such cage support devices is generally performed by fairly invasive methods, and it would be advantageous to devise a less invasive method of performing the complete GOLIF procedure.
The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.